Seconded, as currently UA's non-refundable fares do not give residual value -- so, after buying a flight with the ETC, and then cancelling it to get FFC, if your next flight is less expensive than the FFC, UA keeps the difference. If you use a refundable fare instead, you at least have a shot of being able to get a new ETC generated for the residual value (after deducting the cancellation penalty, if any). This might not work -- in theory, the refund isn't supposed to reset the expiration date, or people could keep an ETC alive indefinitely in this manner -- but recent reports seem to suggest that it will. I probably wouldn't be so bold as to attempt to refund the entire amount -- rather, I'd use the FFC as it was intended and hope that any excess might get rolled into a fresh ETC.